Conventional optical fibre structures are typically based on circular symmetric core and cladding profiles. The introduction of additional micro- and nano-structures greatly enhances the possible functionality of such optical fibres. Such additional structures may be implemented locally (e.g. Bragg gratings, surface gratings) or may be incorporated in the core or cladding structure (e.g. photonic crystal fibres, multicore fibres). Especially hole-assisted fibres have become increasingly interesting for different types of applications not only in optical communication but also for fibre light sources and amplifiers and in optical sensing. Due to holey structures, optical transmission properties in terms of wavefield distribution, numerical aperture or dispersion can be modified, or new light guiding principles like bandgap guiding can be applied. Multicore arrays represent structures where several partial wavefields from separate cores may interact. Local structures on or within a fibre allow local modification of guided wavefields. In this way, e.g., the spectral properties are modified or options for switching are introduced.

A novel tunable microwave notch filter based on air-guiding photonic bandgap fiber (AG-PBGF) is proposed and experimentally demonstrated. The operational principle of the proposed filter is analyzed in detail. Using the character of wavelength-dependent high birefringence of AG-PBGF, the frequency response of the polarization-dependent notch filter can be simply tuned by changing the incident optical wavelength, and its notch depth is dominated by the input azimuth angle. Moreover, the proposed filter is free from the coherence induced by the laser source. Therefore, the magnitude frequency response is robust. A piece of 20-m AG-PBGF is used in the experiment. As expected, the free-spectral range (FSR) changes from 22.4GHz to 8.74GHz when the wavelength from 1570nm to 1584nm and the largest notch depth is more than 40dB.

Guided-wave propagation of sub-ps terahertz (THz) pulses in a highly birefringent plastic photonic crystal fiber has been experimentally demonstrated. The fabricated fibers have exhibited an extremely high birefringence of ~ 0.021 at 0.3 THz.

We report on generation of fundamental soliton using a section of photonic crystal fibers (PCFs) with high nonlinearity and anomalous dispersion. 10 GHz output pulses with 6.108 mW average power and duration of less than 10 ps have been generated from an actively mode-locking fiber ring laser based on PCFs. The spectral of output pulses can be tunable from 1532 nm to 1565 nm. According to the estimated peak power of 6.108×10^-2 W for 10 ps pulse, 1.026 order soliton occurred.

Ultra-stable photonic fiber ring lasers are demonstrated at 10 and 40 Gpulses/s repetition rate operating under an optical-RF feedback mechanism with the in-ring hard pumped optical amplification. Ultra-stability is achieved when the circulating optical power is forced into saturation and hence acting as a distributed saturation absorber. Temporal diffraction with harmonic detuning are also analyzed and experimentally demonstrated. Further the pulse repetition rate of higher than 100GHz is achieved by incorporating an external temporal diffraction fiber length.

A 30nm wavelength-tunable backward dark-optical-comb injection-mode-locked semiconductor optical amplifier fiber laser (SOAFL) with pedestal-free is reported after high-order soliton compression with maximum pulse compression ratio of up to 80. Shortest mode-locked SOAFL pulsewidth of 15 ps at 1 GHz is generated, which can further be compressed to 180 fs after linear chirp compensation, nonlinear soliton compression, and birefringent filtering. The pedestal-free eighth-order soliton can be obtained by injecting the amplified pulse with peak power of 51 W into a 107.5m-long single-mode fiber (SMF), providing a linewidth and timebandwidth product of 13.8 nm and 0.31, respectively. The tolerance in SMF length is relatively large (100-300 m) for obtaining <200fs SOAFL pulsewidth at wavelength tuning range of 1530-1560 nm. By extending the repetition frequency of dark-optical-comb up to 10 GHz, the mode-locked SOAFL pulsewidth can be slightly shortened from 5.4 ps to 3.9 ps after dispersion compensating, and further to 400 fs after second-order soliton compression. The lasing linewidth, time-bandwidth product and pulsewidth suppressing ratio of the SOAFL soliton become 4.5 nm, 0.33, and 10, respectively.

Wavelength tunable and ultra stable pulse generation at 10GHz is experimentally demonstrated using a non-PM, regeneratively mode-locked fiber ring laser. Less than 2.0 ps, nearly transform-limited, sech²-shaped pulses are directly generated with supermode noise suppression ratio over 70dB and RMS timing jitter value less than 162 fs. Dispersion management has been exploited in order to obtain the shortest pulse duration at 1.1ps. The mechanisms for the super-mode noise suppression are also discussed.

We report a three-wavelength Raman fiber laser (RFL) with the equal spaced wavelengths based on partially-degenerated four-wave mixing (PD-FWM) in a highly Ge-doped fiber. The FWM processes in cascaded RFLs reduce the threshold power and improve the slope efficiency for two configurations of three-wavelength RFLs. We show a comparison between two configurations of RFLs characterized by their slope efficiency and their threshold.

This paper outlines recent work at Corning Incorporated on fiber composition design and fabrication of a SBS-managed, large-mode-area (LMA), Yb-doped double-clad fiber for high-power, narrow-linewidth fiber laser applications. Through a detailed theoretical analysis for the SBS threshold in optical fibers, an Aluminum/Germanium (Al/Ge) counter-graded fiber-core composition profile has been proposed and demonstrated for reducing the SBS effect, via the reduced-overlap between optical and acoustic modes in the fiber design. Such Al/Ge counter-graded-composition-profile design overcomes the limitation in a multilayer fiber-core approach, in terms of the low-loss fiber fabrication. The new compositionally SBS-managed, LMA Yb-doped double-clad laser fiber fabricated through the new design, has shown more than ~7 dB improvement in SBS threshold over the conventional LMA fiber design. The new fiber offers exceptionally low passive-loss characteristics, and has been demonstrated with uncompromised high laser efficiency for high-power, narrow-linewidth fiber laser applications.

We describe our recent progress in the fabrication and applications of fiber grating based resonant devices including in-fiber Fabry-Perot etalons and distributed Gires-Tournois etalons.

In this paper, we derive the general condition for the realization of a temperature-insensitive resonance wavelength of a long-period waveguide grating and present numerical examples for gratings formed in polymer channel waveguides. We show that, by controlling the thickness of the waveguide cladding, zero temperature sensitivity can be achieved with core and cladding materials that have significantly different thermo-optic coefficients. To verify our finding, we follow the temperature-insensitivity condition and fabricate a polymer grating with a core material that has a thermo-optic coefficient about twice as that of the cladding material. The temperature sensitivity of the fabricated grating is within ±0.15 nm/°C over a temperature range of ~15°C, which is more than an order of magnitude lower than those of previously reported gratings fabricated with the same materials.

A 1.3-μm vertical-cavity surface-emitting laser (VCSEL) with a fiber Bragg grating (FBG) as an external cavity was developed. VCSELs emit light vertically from the semiconductor substrate. They have a circular output beam and therefore have a merit of easy coupling with optical fibers. Long-wavelength VCSELs in the 1.3 or 1.55-μm bands have recently been developed, which are suitable for long-distance telecommunication using single mode fibers. In this study, we coupled a 1310-nm VCSEL with an FBG as a wavelength-selective external cavity. The FBG was inscribed into a single mode fiber and the reflectivity was 47%. A rod lens was used for coupling of the VCSEL and a fiber. Grating temperature was varied for tuning of the Bragg wavelength. The spectral width without using an FBG was 85 pm FWHM, then the spectral width decreased to 64 pm FWHM by using an FBG at a temperature of 50°C. Further narrowing to 52 pm FWHM was obtained by an optimized diode current. It is expected that the wavelength dispersion in optical fiber transmission can be reduced by using an FBG.

In this work an electrically tunable true time delay line (TTD), useful for phased array antennas, is experimentally demonstrated. The TTD line operates at a single optical wavelength and it is based on a linearly chirped fiber Bragg grating (LCFBG). Continuous TTD is achieved by changing the temperature of the LCFBG. In order to reduce the range of temperatures required for supply high time delay variations, the grating was bonded onto a metallic support and the effect of the thermal apparent strain was considered. The time delay response of the system has been measured with an optical signal modulated with Double Side Band technique at a frequency of 2GHz. The experimental results demonstrate a minimum time delay of 3.1ps employing a temperature controller with a stability of ±0.1°C and a maximum time delay of 96ps over a temperature range of 16-40°C. The time delay-temperature characteristic offers a slope of 3.8ps/°C with a mean deviation from the linearity of 3.5ps. Such a delay line, by operating at a single optical wavelength and by using a simple actuating system, offers many advantages being low cost, compact and reliable. The main limitation to the TTD resolution is the amplitude ripple of the LCFBG and a performance enhancement can be obtained with specifically tailored LCFBG.

We demonstrate LPWG in sol-gel material with replica molding and stamping technique. The grating structures were fabricated on top and bottom of the same ridge waveguide and operate at both communication wavelengths 1550 and 1310 nm respectively.

We constructed a standard measurement setup for polarization mode dispersion (PMD) based on Jones matrix eigen-analysis method. We measured a differential group delay of a 1 m-long polarization maintaining fiber (PMF) and evaluated the measurement uncertainty to be less than 0.6 %. As a transfer standard for PMD, we fabricated mode-coupled PMD artifacts by concatenating the 50 PMF sections with random birefringent axis orientation. Using the standard setup, we certificated the PMD values of the three PMD artifacts to be 0.0884 ps, 0.977 ps, 1.541 ps with the standard uncertainty of 0.4 fs, 16 fs, 23 fs, respectively.

We have developed a thermally tunable module to compensate polarization mode dispersion (PMD) and chromatic dispersion (CD) simultaneously. In this module, twins of linearly chirped fiber Bragg gratings (LCFBGs) are used to compensate PMD and one non-linearly chirped FBG (NLCFBG) is used to compensate CD in 40Gb/s optical fiber communication system. The fiber Bragg gratings are coated with uniform thin metal film, and by changing the applied current through the film, the tunable compensation for PMD and CD is achieved. The fabrications of the LCFBG and NLCFBG are both utilizing the linearly chirped phase mask, making the fiber Bragg gratings easy to obtain.

In this paper, we have numerically investigated the polarization dependent confinement losses in squeezed photonic crystal fibers (SPCFs) by a full vector finite element with anisotropic perfectly matched layers. Numerical results show that single polarization mode transmission can be realized by maintaining large differential loss between the two polarization states. The effect of the structural parameters has also been explored.

Influence of polarization drifts on a novel photonic ADC proposed was calculated theoretically and demonstrated through optical system simulation. A recently proposed polarization-drift free setup was established and it improves the performance of the device.

The impact of polarization dependence loss (PDL) on the degree of polarization (DOP) feedback signal in polarization mode dispersion (PMD) compensation is discussed in this paper. PDL affects DOP only in the presence of PMD. And in the presence of PMD and PDL, DOP relates not only to both the PMD and the PDL vectors, but also to the signal's polarization states. The PDL minimum endangering PMD compensation is determined by the step size of the practical PMD compensating algorithm, and the DGD value in optical fiber systems. DOP could no longer act as the feedback signal in PMD compensation unless PDL in the fiber system has been effectively eliminated before PMD compensation.

In this paper, the DGD (Differential Group Delay) method for beat length measurement of PANDA polarization maintaining (PM) fibers is theoretically analyzed in detailed. And the analysis indicates, regarding the series of silica optical fibers, the error of beat length at different testing wavelength can be ensured less than 2% based on present fiber designs and germanium-doped concentration level. Presently the PMD400 (Polarization Mode Dispersion) analyzer is applied to measure the beat length of polarization maintaining fibers at Yangtze Optical Fiber and Cable Company. Lots of test results shows the DGD method is very reliable, convenient and nondestructive. In practical, the relative deviation of beat length at different wavelength can be kept under 1.5% below based on a number of experimental data. Therefore, the DGD of a PM fiber can be tested at a definite wavelength, such as 1550nm, and then the beat lengths at other operating wavelength can be got according to the relationship between beat length and operating wavelength.

This paper reviews recent progress and experiment and modeled results on dual air hole-assisted polarizing fibers which can act as either Single Polarization (SP) fiber or Polarization Maintaining (PM) fiber. Dual air hole-assisted fiber design provides both SP and PM characteristics for the same fiber at different wavelength range. SP operating windows centered at wavelength from 980 nm to 1550 nm with bandwidth ranging from 24 nm to 63 nm are demonstrated. Various properties of the fibers are studied. We explored bend and length dependence of SP window which enables fining tuning in actual device application. We also investigated SP and PM characteristics over wide range of temperature, such as fundamental cutoff wavelength, extinction ratio and birefringence. It was found that hole-assisted polarizing fiber provides less temperature sensitivity compared to stress member-assisted polarizing fiber. Lastly, Ytterbium (Yb) doped SP fiber, which combines gain medium and polarizer into single element was realized. Significant benefits can be achieved by using Yb-doped SP fiber in application such as fiber laser or amplifier, which requires linearly polarized output.

As an application in the backlight system of small LCD display, we realized a pure white light source by mixing red, green, blue (RGB) lights using a 3 X 3 Hard Plastic Cladding Fiber (HPCF) coupler. We also proposed the 0.44 inch LED backlight system with these fiber-optic pure white sources and characterized its illumination characteristics. Using optimized fusion-tapering technique, we fabricated HPCF coupler which combines three input lights over the circularly formed waist. HPCF has the core diameter of 200 μm and clad diameter of 230 μm. The fabricated 3 X 3 HPCF coupler has the perfect uniformity of about 0.3 dB, low insertion loss of 5.5 dB, and low excess loss of 0.8 dB, which shows excellent uniform power splitting ratio. In order to improve the transmission performance, The RGB chip LEDs were butt-coupled directly to the ferruled input ports of the coupler and packaged by TO46-can type. In the produced white color by HPCF coupler, the photometric brightness at the circular endface of outputs of HPCF coupler was in a rage of 10062 ~ 10094 cd/m². The fiber optic white color combiner provides tunable white sources excluding heat source and having thickness of 200 μm. We also proposed a 0.44 inch LED backlight system with these fiber-optic pure white sources. With the proposed device, we obtain the improved uniformity in luminance distribution and wide color gamut by using the white light mixing red, green and blue lights.

We developed the primary components applicable to HPCF links for short reach (SR) and very short reach (VSR) data communication systems. We fabricated 4x4 HPCF fused taper splitter, HPCF pigtailed VCSEL and PIN photodiode for high speed short reach communications and characterized back to back transmission performance of the link composed of these components by measuring eye diagrams and jitters. Adapting the fusion-tapering technique for glass optical fiber, we successfully fabricated a 4x4 HPCF fused taper coupler. The HPCF with a core diameter of 200μm and an outer diameter of 230μm had step refractive index of 1.45 and 1.40 for the core and the clad. The optimized fusion length and tapering waist which make minimum insertion loss of about 7dB and uniform output power splitting ratio with less than 0.5dB are 13mm and 150µm, respectively. As a light source for VSR networks, we chose a vertical cavity surface emitting laser (VCSEL) and developed a package with a HPCF pigtail. After positioning VCSEL and HPCF that made a minimum coupling loss, we glued the HPCF inside ceramic ferrule housing. In HPCF-PIN PD packaging, we added a micro polymer lens tip onto the HPCF ends to match the mode field area to the sensitive area of GaAs or InGaAs PIN PD. Coupling between a PIN PD chip and the lensed HPCF was optimized with the radius of curvature of 156µm with a low coupling loss of 0.3dB, which is compatible to conventional MMF-PD packaging. For 1.25 Gbps data rate, the eyes adequate to eye mask in gigabit Ethernet were wide open after all HPCF transmission link and no significant power penalty was observed.

In this paper, we describe a development of a polarization-maintaining fiber by PCVD based process which can be used in the high precision gyroscope and present its measured properties. This kind of fiber is designed as the reduced cladding PMF. The fabrication of the polarization-maintaining fiber is based on the PANDA PMF PCVD based process. Thus, with the reduced cladding, the fiber has better bending properties. Fabrication by the PCVD process, the fiber also has good longitudinal uniformity and a low-loss about 0.374dB/km @ 1310nm, 2.0mm beatlength and -30dB/km crosstalk. It's environmental performance of crosstalk is also good for fiber optic gyroscope. These better properties make this fiber can be used in the high precision gyroscope system.

Differential mode delay (DMD), chromatic dispersion, and modal dispersion measurement techniques for a multimode optical fiber based on optical frequency domain reflectometry are presented. We have used the principle of a conventional OFDR with a tunable external cavity laser and a Mach-Zehnder interferometer. We have compared our measurement results with those obtained using a traditional time-domain measurement method.

Planar lightwave circuits (PLCs) are waveguide devices that integrate fiber-matched optical waveguides on Silicon or glass substrate to provide an efficient means of interaction for the guided-wave optical signals. PLCs provide various important functionalities for optical wavelength division multiplexing (WDM), time division multiplexing (TDM) systems and subscriber networks. This paper reviews the recent progress and future prospects of PLC technologies especially in FTTH and GMPLS (Generalized Multi-Protocol Label Switching) systems.

We describe a high isolation thin-film filter coated on a GRIN lens surface for triple-play services. High isolations of 60 dB and 43 dB between 1480 nm and 1550 nm bands in transmittance and reflection ports are achieved by use of originally developed ion-beam sputtering deposition machine.

A novel approach for optical beam distribution into a 2-dimensional (2-D) packaged fiber arrays using 2-D Dammann gratings is investigated. This paper focuses on the design and fabrication of the diffractive optical element (DOE) and investigates the coupling efficiencies of the beamlets into a packaged V-grooved 2x2 fibre array. We report for the first time experimental results of a 2-D optical signal distribution into a packaged 2x2 fibre array using Dammann grating. This grating may be applicable to the FTTH network as it can support sufficient channels with good output uniformity together with low polarization dependent loss (PDL) and acceptable insertion loss. Using an appropriate optimization algorithm (the steepest descent algorithm in this case), the optimum profile for the gratings can be calculated. The gratings are then fabricated on ITO glass using electron-beam lithography. The overall performance of the design shows an output uniformity of around 0.14 dB and an insertion loss of about 12.63 dB, including the DOE, focusing lens and the packaged fiber array.

When diffractive gratings are used to split a beam of ultrashort laser pulses, due to its broad spectral bandwidth, the spots split will be distorted because of chromatic dispersion. Our ambition is to construct a novel pulse splitter system that is possible to compensate for chromatic dispersion during fanning-out of laser beam by diffractive gratings. Moreover, the proposed design can reduce the size of the splitter system and obtain higher diffraction efficiencies.

Two-dimensional optical low pass filter (OLPF) was designed, fabricated and tested in our lab. The modulation transfer function (MTF) of OLPF shows that cut-off frequency is 96.15lp/mm in x and y direction, which is satisfied with our design. The transmissions in the visible and infrared regions of the spectrum are mostly above 95% and less than 2%, respectively. The error of every plate thickness is tested less than 0.34% by the experiment of pulse response. The spatial frequency test results show that our device has good low filter performance, matches with the solid state image sensor and well restrains the moire effect and false colors distortion.

The wideband, low loss transmission capability of optical fiber links has led to an ever-increasing interest in their use for the distribution of radio signals for applications such as broadband wireless access networks, sensor networks and radar systems. For many applications, it is highly desirable that the microwave signals can be processed in the optical domain without extra optical to electrical and electrical to optical conversions. In this paper, recent advances in all-optical RF signal processing, including all-optical microwave filtering and all-optical microwave mixing, for radio over fiber networks applications are reviewed.

We describe recent advances in optical communication components, modules, and subsystems based on planar polymer technologies. The dynamic organic photonic integrated circuits exhibit ultra low power consumption through thermo-optic actuation for switching, routing, and tuning. The components (switches, optical cross-connects (OXC), variable optical attenuators (VOA), tunable couplers, etc.) have state-of-the-art performance, meet reliability requirements in the telecommunication industry including Telcordia GR-1209 and GR-1221 qualification, and are broadly deployed in the field. The modules and subsystems include variable multiplexers (VMUX) and reconfigurable optical add/drop multiplexers (ROADM), and they meet the requirements of Telcordia GR-1312 and GR-63 protocols.

We demonstrate the possibility of confining light in a submicron silica core by introducing a Bragg multilayer cladding. 1 μm-core Bragg tapers with mode field diameters about 1.1 μm for 850 nm wavelength are successfully fabricated by a sputtering technique combining with tapering method using a traveling burner. Simulation of the mode intensity profiles for both our devices and air cladding silica fibers are made by a beam propagation method. Bragg fiber tapers show stronger confinement than silica glass tapers. The ultra-small core Bragg taper device will be a good candidate as the mode coupler for nano-optical devices.

To enhance the functionality and flexibility of a multiwavelength fiber laser, characteristics such as the tunability of the lasing wavelength, the wavelength spacing and the number of channels should be investigated simultaneously. We have demonstrated a channel spacing and wavelength tunable multiwavelength fiber ring laser based on semiconductor optical amplifier and a novel tunable polarization-diversity loop configuration (PDLC)-based comb filter. The tunable PDLC-based comb filter would be composed of a polarization beam splitter and three wave plates (one quarter wave plate and two half wave plates) and a polarization differential delay line (DDL). Channel spacing can be controlled continuously by using a motorized polarization differential delay line. And wavelength can be simultaneously changed by controlling wave plates. The PDLC-based comb filter has the advantages of the input polarization independence and simple tunability. By employing the comb filter in the laser system, multiwavelength operation of up to 25 laser lines with the signal-to-noise ratio over 25 dB and 0.8 nm wavelength spacing has been demonstrated at room temperature. Also, we could achieve the increased output channel power of the laser while reducing the number of channels. The results show that the multiwavelength operation is even and stable. And we could achieve the output spectra of tuned wavebands with channel spacing of 1.6 nm and 0.4 nm when the semiconductor optical amplifier is driven with the injection current of 160 mA while adjusting a half-wave plate at each tuning set. As a result, the shift of lasing wavelength and wavelength spacing were continuously controllable in this system.

Theoretical and experimental results are reported for a twin-core microstructured polymer fiber. A full-vectorial numerical method based supermode theory is applied in the symmetrical structure to obtain the interference between the even and odd modes. The wavelength dependence of the coupling length is measured, and compared to calculations using a full-vectorial numerical method. Both results show good agreement.

We propose a low-cost, general-purpose fiber Bragg grating (FBG) cavity sensing technique, where optical picosecond pulses generated from a self-seeded Fabry-Perot laser diode are used to interrogate a fiber cavity formed with two chirped FBGs and the optical loss in the cavity is determined from the peak power ratio of the first two pulses reflected from the cavity. This technique does not require intensity referencing and the sensor output is insensitive to drifts in the center wavelengths of the FBGs. We demonstrate this technique experimentally with a long-period fiber grating (LPFG) placed in the fiber cavity as a refractive-index sensor. The results from the cavity-loss measurement are consistent with the wavelength-shift measurement of the LPFG in response to a change in the surrounding index. This technique is applicable to general intensity-based sensors and has the potential to be further developed for remote sensing of a wide range of physical or chemical parameters. It also provides a new way of converting the wavelength shift of an LPFG sensor into an intensity-based signal for easy processing.

This paper presents a review of the development of long-period waveguide gratings (LPWGs) with focus on the realization of various kinds of tunable devices, such as band-rejection filters, variable attenuators, band-pass filters, and add/drop multiplexers. A number of specific examples are given to demonstrate how the geometry and material flexibility of the optical waveguide technology facilitates the design of widely tunable LPWG-based devices. LPWG is evolving into a versatile waveguide structure for the implementation of a wide range of optical functions.

To reduce the crosstalk of the polymer waveguide optical switches, waveguide attenuators are integrated with the switch on the same substrate. The switch and attenuator shares a single connected electrode which is controlled by a single current source. Due to the simple structure of the integrated attenuator, the device length is reduced to 10 mm so as to provide low insertion loss of 0.8 and 1.1 dB for 1300 and 1550 nm, respectively. Further radiation of the remained optical signal on the switch-off branch is induced by the integrated attenuator so that the switching crosstalk is reduced to -70 dB with an applied electrical power of 200 mW. The low crosstalk is maintained for the environmental temperature range of -10 to 55 °C.

We demonstrate long-period gratings in silicon oversized-rib optical waveguide. The fabricated long period gratings show the maximum attenuation of 5.8 dB and the resonant wavelength shift of about 0.07 nm/°C.

The cost-effective and repeatable technology for integration of polymer multimode waveguide and out-of-plane 45° reflector mirrors is developed. This method is cost-effective, repeatable, robust, and fully compatible with the standard manufacturing processes for a 90° optical bending structure. The basic concept of the technology for integration of waveguide and out-of-plane 45° reflector mirrors is as follows; 1) The positively patterned master in order to mold waveguides is manufactured by using photolithography and Deep RIE (Reactive Ion Etching). And the master is polished to obtain 45°-inclined plane. 2) Both sides of the positively patterned master are divided into three parts by using a sawing machine. One is a center master (main-master) with a positively patterned waveguide and the others are side masters (sub-master) without a pattered waveguide. The main master and sub-master turned over get back together again. 3) The negatively patterned PDMS master to be able to mold simultaneously both waveguide and out-of-plane 45° reflector mirrors is manufactured through pouring PDMS gel into master and thermally curing the PDMS master. 4) The multimode tapered waveguides with out-of-plane 45° reflector mirrors are simultaneously embossed by using PDMS master. The UV (Ultraviolet) curable material is organic-inorganic hybrid material (HYBRIMER, core index: 1.51, clad index: 1.48). The transmitter module is constructed on a MOB. The MOB was employed for several purposes; to align optical module passively, to use as heat sinker and also to support the boards. On this MOB, 1×4 arrays of vertical-cavity surface-emitting laser (VCSEL) and Tapered Waveguide with 45° reflector mirrors are integrated. The height and width of waveguide's core are 100 μm, 60 μm respectively and the pitch is 250 μm. The transmission access lines in transmitter are designed considering differential impedance matching for high-speed operation. We measured the insertion loss of this transmitter module using a 62.5 μm graded index fiber. The average insertion loss value is roughly about 7dB.

In this paper, we describe the cost-effective and simplified fabrication of an index modulation type buried waveguide using laser direct writing. Our studies have a potential of manufacturing waveguides on an uneven surface and a large area because there is no need for photo-mask, etching and development processes. We used organic-inorganic hybrid materials (HYBRIMER) for the fabrication of the waveguides, which have a high transparency from a visible region to an infrared region. We exposed the core layer (HYBRIMER) to a focused laser beam after a one-step spin coating process on a buffer layer. The silicon oxide was used as a buffer layer. The refractive index of the HYBRIMER film is increased by exposure from a laser beam. Therefore, the refractive index of the exposed region is higher than that of the unexposed region, which forms the index modulation type waveguide without an etching process. The fabricated waveguide channels were baked at 120°C during 3hrs for stabilization of the organic and inorganic networks. The laser direct writing apparatus was used to produce the pattern of waveguide channels. This system consists of a He-Cd laser radiating 325nm beam, high-resolution computer-controlled translation stages and a video camera that images the sample onto a monitor. The pattern of the waveguide channel was written using various writing speeds to optimize the writing condition. The core section of optimized waveguides was a rectangular shape and the core dimension was 7μm wide and 8μm high. The refractive index is increased from 1.495 to 1.5 after exposure. The difference of the refractive index between the core and cladding was approximately 0.33%. The insertion loss of the waveguides was measured by cut-back method using a single-mode fiber as an input tip, a multimode fiber (50 μm GI) as an output tip, and a 1310nm wavelength laser light source. The insertion loss shows a linear relationship with the length of the waveguide. The propagation loss of the buried waveguide was approximately 0.3dB/cm at a wavelength of 1310nm.

The self-image profiles in a multimode waveguide can be estimated from the phase relations of the guided-modes. However, in MMI theory, the propagation constants of each guided-mode are defined as a perfectly confined condition. Because of the effect of the Goos-Haenchen shift, there are large phase differences for each guided-mode between the predictions of MMI theory and the actual phenomena. Because the relative phases of the guided-modes are not the same as the theoretical ones in a multimode waveguide, it is possible that an undefined self-image can be produced. In this paper, such a phenomenon is called the 'pseudo-self-imaging phenomenon'. This phenomenon can be observed in both the simulation and the experimental results. The excess loss has been measured, and the results are the same as -0.5dB for both the 1st 0-dB self-image and the 1st pseudo-self-image. These results may have been occurred by the phase mismatch of the guided-modes. The extinction ratios are also measured, and the results are 15.5dB for the 0-dB self image and 16.2dB for the pseudo-self-image. From the result, it is shown that the pseudo-self-image is formed after the 0-dB self-image and the pseudo-self-images' intensity can be higher then the 0-dB self-images.

We propose and experimentally demonstrate a new and simple chromatic dispersion controller based on the uniform FBG with the symmetrical bending technique. Dispersion compensation has been one of the most significant issues for the high-speed optical communication systems. Chirped fiber Bragg gratings (CFBGs) have been of interest in the applications to dispersion compensating devices due to their versatile advantages like fiber compatibility, polarization insensitivity, low nonlinearity, low loss and so on. To provide the dispersion tunability of CFBGs, the great efforts based on thermal heater, tapered fiber by etching, stacks of piezoelectric actuators, and adhesive package with gradient thickness. The previous methods, however, have the drawback of the center wavelength shift into the longer wavelength. To solve the limitation of previous methods, a range of methods to induce the wide tuning range of dispersion without the center wavelength shift have been intensively investigated. Using a divided thin-film heater with a peltier element, the tunable dispersion compensator based on a fiber grating was reported. To prevent the center wavelength shift, two heating elements like a thin-film heater and a peltier element were used. However, it has the complex structure and the small tuning range of dispersion. Most of methods to improve the dispersion controllability of a fiber grating without the center wavelength shift are based on the symmetrical bending method. To induce the symmetrical bending along a fiber grating, versatile schemes based on moving block, curved fiber gratings attached on a plate, and a rotational stage with pivots were proposed. In this letter, a new method to control the chromatic dispersion of uniform FBG is proposed and experimentally demonstrated. We precisely controlled the dispersion value of uniform FBG by inducing the linear strain gradient based on the proposed tuning device. Since the symmetric bending of the flexible cantilever beam with the uniform FBG is induced by the interaction between two translation stages and a sawtooth wheel, the tension and compression caused by the symmetrical bending can effectively control the properties of the fiber grating like bandwidth and group delay. We successfully obtain the wide tuning range of chromatic dispersion of the uniform FBG (from 312.6 ps/nm to 35.9 ps/nm) without the center wavelength shift, which is less than 0.02 nm. We also suppress the group delay ripple as low as ~ ±5 ps. And we also demonstrate the application of the proposed tunable dispersion compensation technique to the tunable repetition-rate multiplication and obtain high quality pulses at repetition-rates in the range of 20 ~ 40 GHz from an original 1.8 ps, 10 GHz soliton pulse train.

In this paper, the double-layer gratings recorded in photopolymer films for the optical demultiplexer is presented. The channel spacing of 0.4nm, the channel uniformity of 3.5 dB, the 3dB-bandwidth of 0.12 nm, and the channel crosstalk of -20dB is experimentally obtained.

A novel erbium-doped fiber laser with high extinction ratio of more than ~60 dB based on a tunable bandpass filter is proposed and experimentally demonstrated. The proposed tunable filter consists of fiber Bragg gratings incorporating Sagnac loop interferometer configuration.

An optical bandpass filter with two ultranarrow transmission bands, based on fiber Bragg grating (FBG), is presented. The wavelength spacing can be easily changed through controlling the separate distance between two introduced π phase shifts. When it is served in a fiber ring laser, the stable dual-wavelength lasing with ultranarrow wavelength spacing is achieved. This novel device will find potential applications in the generation of various high-frequency microwave signals, fiber sensing, etc.

A novel scheme is proposed to transform an optical pulse to a millimeter-wave frequency modulation pulse by using a fiber Bragg grating in radio-over-fiber system. The Fourier transformation method is used to obtain the required spectrum response function of FBG. Based on this target spectrum response function, the cases for a weak fiber grating and strong fiber grating are analyzed and the corresponding refractive index distributions are obtained. The performances of the fiber gratings are also studied by a numerical simulation method for an ultra-short pulse transmission.

The optical fiber fabrication technology based on Bismuth oxide (Bi₂O₃) material has advanced significantly in recent years and has resulted in the production of a variety of high quality of Bi₂O₃ based optical fibers: for example, rare-earth doped Bi₂O₃ fibers and highly nonlinear Bi₂O₃ fibers (Bi-NLF). One of the most striking and attractive possibilities offered by the Bi₂O₃ based optical fibers is the opportunity to implement a range of nonlinear optical signal processing devices with only a meter or less length of the fiber due to its ultra-high material nonlinear coefficient, which is 100 times higher than that of silica. The state-of-the-art Bismuth Oxide based nonlinear optical fiber technology for nonlinear optical signal processing devices is reviewed from a viewpoint of possible application for telecommunications.

A new method to evaluate the image quality of the fiber bundle using digital micro-mirror device (DMD) along with accessory light modulator package (ALP) is proposed. We have demonstrated that some characteristics of fiber bundle, such as an extent of blurring, gray-level degradation and color aberration can be evaluated by using a single device DMD-ALP, and we have also proved capability of micron-order analysis. Moreover we measured the transmitted image contrast of the fiber bundle using some line pairs made by DMD-ALP, which can be more convenient than previous methods.

We propose a novel efficient dispersion compensating filter that is relatively simple and much less expensive to implement. It is a multicavity Gires-Tournois etalon based all-pass filter and the length of each of the cavities is slightly mismatched. We present a theoretical study of the filter for chromatic dispersion compensation. Our simulation results show that a linear group delay response can be obtained by properly choosing the mismatched cavity length and the chromatic dispersion value can be controlled by suitably adjusting the reflection coefficients of the mirrors. For applications in fiber disperison compensation, the disperson slope can be achieved by slightly modulating the reflection coefficients of the reflectors relative to wavelength.

The area of integrated optical circuits has been undergoing rapid development and will have huge potential in the future due to the important applications of fiber communication systems and optical interconnects. A significant challenge of optical circuits lies in increasing circuit density while miniaturizing the devices. Couplers are important parts in integrated optical circuit and high efficiency compact couplers are in great demand. We report here the binary blazed grating coupler that can commendably solve these problems. The binary blazed grating is composed of subwavelength pillars with uniform height, which can be easily fabricated by only one etching step. It is found that this element substantially outperforms standard grating. Because of its high coupling efficiency and compact structure, the binary blazed grating coupler exhibits excellent performance in fiber-to-waveguide/waveguide-to-fiber coupling, waveguide-to-waveguide coupling, chip-to-chip vertical coupling, etc. In this paper, a basic design principle of the binary blazed grating coupler is presented, and some improved structures to enhance the coupling efficiency are proposed and estimated. The FDTD method is utilized to simulate and design the binary blazed grating operated under TE polarization for 1.55μm. With our optimization design, the coupling efficiency can be largely increased.

Air guided single mode propagation of THz radiation in a photonic crystal waveguide has been experimentally demonstrated. The photonic crystal waveguide has been fabricated by introducing an air defect at the center of the air/Si 1D photonic crystal.

We demonstrate a simple UV-writing technique for the fabrication of buried waveguides using a UV lamp as the source and benzocyclobutene (BCB) and epoxy OPTOCAST 3553 as the waveguide materials. We find that the refractive index of the core material BCB can be increased by as much as 0.01 after UV exposure, while the refractive index of the cladding material epoxy OPTOCAST 3553 is not affected by the UV light. Based on these material properties, buried channel waveguide devices are formed by UV irradiation of an epoxy-clad BCB slab waveguide through a mask. We demonstrate the technique with a straight single-mode waveguide, a Y-junction waveguide branch, and a long-period waveguide grating. The propagation loss of the waveguide fabricated by this technique is 1.8 dB/cm at 1550 nm and the polarization-dependent loss is 0.15 dB/cm.

A novel single-mode single-polarization (SMSP) photonic crystal fiber using resonant absorption effect has been put forward and analyzed for the first time, to our knowledge. A full-vector finite element method with perfectly matched layers is employed to investigate the characteristics of the fiber. The numerical results predict that very efficient SMSP operation can be achieved with both high bandwidth and high extinction ratio at low loss penalty. The effects of the fiber structural parameters have been explored, which will provide useful directions for the design and fabrication of the fiber. The research results will be instructive for the realization of new high performance SMSP fibers.

The effect of initial frequency chirp is theoretically investigated in photonic crystal fibers with two zero-dispersion wavelengths. Based on numerical simulations, it is shown that there exits an optimal propagation distance whether input pulse is chirped or not, where spectrums have maximal bandwidth. Furthermore, contrary to the complicated spectrum structure generated by negative-chirped pulse, positive linear chirp enhances supercontinuum generation and spectrum is much more regular. The efficiency of four-wave mixing is also improved because of initial positive chirps, and for enough large chirp values the incident pulse energy in the anomalous dispersion region is almost thoroughly transferred to the visible and near-infrared regions outside two zero-dispersion wavelengths.

This paper reviews recent progress on high-speed technologies for optical transmission systems in the IP and FTTH era. First, we describe our latest research results of 160 Gbit/s optical time-division multiplexing and demultiplexing experiments. The all-optical time-division multiplexer is realized as a hybrid integrated device consisting of planar lightwave circuits (PLC's) and highly-nonlinear periodically-poled lithium niobate (PPLN) waveguides while the demultiplexer is realized as a hybrid integrated device consisting of PLC's and semiconductor optical amplifiers. A new type of all-optical switch that uses a photonic crystal nanocavity and an all-optical flip-flop circuit that is composed of two-port resonant-tunneling filters based on a two dimensional photonic crystal slab with triangular air-hole lattice are shown. Finally, the possibility of over 100 Gbit/s all-optical signal processing is discussed for high-speed optical transmission systems.

The effect of external feedback on an isolator free transmitter was investigated experimentally by measuring relative intensity noise (RIN). The experiments were done under the possible conditions that might happen during operation such as external reflection and temperature change. In addition to that, the effect of reflection depending on the types of source which DFB and FP LD are widely used for that. Finally, LD to Fiber alignment under external reflection was demonstrated. It was found that the effect of external reflection was dominant factor compared with temperature change and FP LD is less affected by reflection than DFB LD. The maximum RIN occurs at the maximum coupling position of LD and fiber and the minimum RIN exists near the maximum coupling position, which can be used to optimize the coupling and RIN tolerance according to the alignment position by changing the lens focal length.

Recent years have seen an explosive increase in the application of inter-satellites laser communication system. Considerations make phased arrays an attractive target for optical communication applications. This paper proposes a novel telescope array for inter-satellites laser communication and investigates phased telescope arrays to be employed in receive terminals of free-space laser inter-satellites communication links. Potential advantages over single monolithic telescopes consist in non-mechanical adaptive fine pointing of the mainlobe and a reduction of terminal volume, mass and cost. First, the basic function, the interfaces, and the performance parameters of one telescope are given. Next, the structure of a receive telescope array are described, and then the performance parameters of this telescope array are discussed. The different performances including antenna gain and pattern of optical antenna and telescope array in inter-satellites laser communication system are given in this part. A quantitative assessment reveals that arrays using coaxial beam superposition are best suited for optical data communications. Based on this finding, the main characteristics of superimposing telescope arrays are calculated. And calculations prove that, in practical applications, telescope array has better performance than one telescope used in laser inter-satellites communication, and even more, the influence of incoherent background radiation is negligible. The analyses results show that smart antenna is better than optical antenna in this communication system. In many important aspects of phased array design, we will consider 1) Frequency Synchronization and 2) Beam steering as being of primary importance to the present analysis. Frequency synchronization is necessary for proper beam spatial coherence, while beam steering is critical to how this cohered beam is pointed in a desired direction. We will address system performance and implementation aspects of both issues in fiber optic control. Three basic architectures for beam steering control via optics have been reported and proposed.

Based on the characteristic of vector waves which taken part in the multiple beams interference in the focal field of concave grating demultiplexer, the reversibility between emission efficiency and receiving efficiency of the optical waveguides, and the amplitude superposition theorem of multiple beams interference, an original analytic expression of simple spectral response efficiency of concave grating demultiplexer is derived. As the spectral distribution of the actual input optical signal is considered, the Gaussian function spectral distribution for example, the actual responsibility and crosstalk of the concave grating demultiplexer for this input optical signal are introduced. Several analytic expressions offer some useful foundation and novel method for analyzing the responsibility and crosstalk of concave grating demultiplexer. A computing instance of concave grating demultiplexer is given, this instance shows that the actual response efficiency characteristic curve which engaged the Gaussian function spectral distribution of input optical signal is smoother than the simple spectral response efficiency characteristic curve which ignored input optical signal spectral width, the smoothness of actual response efficiency characteristic curve and the actual responsibility are dependent on the spectral half width at one of e square of the maximal intensity of actual input optical signal.

A chirped, phase-shifted structure is demonstrated for compact multi-wavelength DFB fiber laser at room temperature for the first time. The chirped structure provides separated resonance cavities and then the stable multi-wavelength operation. The equivalent phase shift method is demonstrated to realize the desired chirp and phase shifts simply and flexibly. A 44pm-spaced, dual-wavelength DFB fiber laser is then achieved experimentally, which is the narrowest spacing ever reported for a compact multi-wavelength fiber laser.

Dual locking ranges in a harmonic mode-locked fiber laser with a birefringence cavity is reported in this paper. Experimental results clearly show the existence of two separated locking ranges in the vicinity of the 834th harmonic of the fundamental frequency. Theoretical explanation is given. Theoretical estimation of the locking range agrees well with the experimental result. Simulation also reproduces the experimental results.

In this paper, we demonstrate a novel stabilization scheme of actively harmonically mode-locked Erbium-doped fiber lasers (ML-EDFLs) by using highly nonlinear fibers in the cavity. 2 and 4 wavelengths anchored on ITU-T standards with 100 GHz channel spacing are successfully generated without gain competition. The amplitude fluctuation and timing jitter are measured to be less than 1% and 100fs, respectively.

We fabricated erbium-doped fiber ring laser with a new structure that can operate in C- & L-band wavelength region in the optical communication band. We performed the absorption spectroscopy of acetylene (¹³C₂H₂) and hydrogen cyanide (H¹³C¹⁴N) by using a low noise erbium-doped fiber ring laser and measured absorption spectra of more than fifty transition lines of these gases with an excellent signal to noise ratio (SNR). The wavelength of this laser can be continuously tuned over 102 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity with a novel cavity structure and the optimal gain medium length. The acetylene cell and the hydrogen cyanide cells were fabricated with gas pressure of 120 torr and 250 torr and length of 5 cm and 15 cm, respectively. The pressure broadening coefficients of acetylene transition lines are obtained using this fiber ring laser and an external cavity laser diode.

A coupling-ratio controlled wavelength tunable L-band erbium-doped fiber laser with tuning range of 45nm (1567 - 1612 nm), quantum efficiency of 42%, power conversion efficiency of 37%, tuning resolution of 0.3 nm is reported. The wavelength-tuning is achieved by a tunable band-pass filter (TBPF) or by adjusting the tunable-ratio optical coupler (TROC) without TBPF because of the difference of intracavity loss. The output wavelength can be tunable in the full L-band with TBPF, from 1567 to 1612 nm, and the pulse-width is <14.2 ps. Specially, during the wavelength-tunable process without TBPF, the modulation frequency of about 1 GHz remains unchanged and near-transform-limited pulses are generated by linear compression with 32.5 m single mode fiber (SMF) under 10% output coupling ratio.

A dual-wavelength erbium-doped fiber (EDF) variable ring laser using a fiber acousto-optic tunable filter (AOTF) and highly nonlinear fiber (HNLF) is demonstrated. Stable and variable lasing wavelengths were achieved by electronically adjusting the AOTF settings.

Build-up process of the broadband continuous-wave supercontinuum Raman lasing (CWSCRL) in a fiber ring cavity is reconstructed theoretically through simulation based on the generalized nonlinear Schrodinger equations in the spectral domain. The physical mechanism of the CWSCRL is revealed as a combined effect of light amplification by stimulated Raman scattering and spectral broadening by four wave mixing in the view of the spectral domain. Detailed analysis as well as experimental confirmation shows that broad and flat spectrum can be achieved mainly by assigning the pumping wavelengths so that the first Raman Stokes wavelengths occur at both sides of the zero dispersion wavelength of the highly nonlinear dispersion-shifted fiber in the ring cavity, while optimization in pump power also matters. Different time structures of the Raman lasing are determined by the dispersion at the first-order Raman Stokes light wavelengths.

Light showing extremely slow propagation (known as "slow light") can produce various effects such as compression of optical signals, buffering, convolution integral calculation, beam forming, enhancement of optical absorption, gain, non-linearity, and so on. To generate such light, very large material and structural dispersions are used. Photonic crystal waveguides are good candidates for many device applications since they can easily generate slow light at room temperature. This paper discusses the potential of slow light devices while explaining some critical issues, such as the delay-band product and the dispersion compensation.

Planar lightwave circuits (PLC) based on nanophotonic waveguides are becoming more and more attractive because of their ultrasmall sizes and possibility for realizing large scale monolithic integration with a very high integration density. In this paper we discuss two attractive types of nanophotonic waveguides based on dielectrics or metals. For the dielectric type, a silicon-on-insulator (SOI) strip waveguide is considered, and ultra-compact photonic integrated devices such as polarization-insensitive arrayed waveguide grating (de)multiplexers are obtained. Based on the fact that light can be confined tightly in a single interface between a metal and dielectric, a surface plasmon (SP) waveguide can offer a tight confinement for the light field. The cross-sectional size of an SP waveguide could be pushed down to tens of nanometers, i.e. beyond the diffraction limit. An accurate anaylysis for an SP waveguide formed by a dielectric nano-trench in a metal is presented. A novel subwavelength index-guided multimode plasmonic waveguide is introduced and an ultra-compact MMI power splitter is designed.

We fabricated various microscopic optical devices using photonic crystal slab and Si-wire waveguides and demonstrated their fundamental characteristics. We demonstrated a channel-dropping filter with a photonic crystal slab point-defect optical cavity. Wavelength resolution of less than 1.5 nm and signal dropping efficiency of more than 90 % were obtained for a 20-μm-square device. We also demonstrated an optical add/drop multiplexer with Bragg grating reflectors made from Si-wire waveguides. Its dropping wavelength bandwidth was less than 2 nm, and the center wavelength of the dropped optical signal could be tuned by thermo-optic control using a microheater formed on the Bragg reflector. Using Si-wire waveguide, we also demonstrated thermo-optic switches by forming a micro heater on a branch of a Mach-Zehnder interferometer constructed from the waveguides. In this switching operation, we observed an extinction ratio of more than 30 dB, switching power of less than 100 mW, and switching response speed of less than 100 μs using a 1 × 2 optical switch with an 85 × 30 μm² footprint. Using the 1 × 2 optical switch elements, we also fabricated a compact 1 × 4 optical switch and demonstrated its fundamental operation.

A novel interrogation scheme for multiplexing the sensors based on long-period grating (LPG) Mach-Zehnder interferometers (MZIs) is proposed. Each LPG-MZI is formed by a pair of cascaded identical LPGs and induces an additional optical path difference (OPD) proportional to the centre-to-centre interval between the two LPGs. A sub-reflectogram including sensing information can be achieved when the OPD induced in one LPG-MZI is compensated by scanning one arm of a Michelson interferometer to a certain range. For multiple sensors, the grating intervals of different LPG-MZIs are set to different values to ensure that their sub-reflectograms can be well separated in time domain. The spectral response of the LPG-MZI is reconstructed from the corresponding sub-reflectogram with a fast Fourier transformation. Applications of the bending and temperature monitoring are demonstrated by measuring the signals in time domain and wavelength domain, respectively.

This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Spectral characteristics were measured for 850nm VCSELs to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The performance of 850nm VCSEL/FFPI systems was compared with their counterparts using 1300nm distributed feedback (DFB) lasers.

We report the study of chromatic dispersion ripples in birefringent crystal-based optical interleavers. The simulation indicates that for a 99.8% transmittance AR coating surface, the chromatic dispersion ripples caused by the Rhomb etalon effect could be as high as ±30 ps/nm. The experimental results are in agreement with the simulation results. We also demonstrate a practical approach to eliminate the chromatic dispersion ripples to be coupled into the output collimators. The overall interleaver chromatic dispersion, of less than 15 ps/nm within the passband, is demonstrated.

A precise measurement method for linewidth enhancement factor of SOA by Sagnac interferometer when considering XGM is presented. It needs neither spacial interference nor optical spectrum analysis, has simple configuration and better measurement stability than existing methods.

We describe optical trap lattices, their manipulation, and optical trapping using the digital micromirror device (DMD)-accessory light modulator package (ALP). The proposed device flexibly controls the trap profile, array dimension, hopping over trap lattice, and steering therewithin. In order to generate optical trap lattice with Gaussian intensity profile, desirable input electronic images with LP₀₁mode of single mode fiber to the DMD-ALP was loaded, which formed 2-dimensional optical trap lattice with Gaussian intensity profile. We generated 2-dimensional multiple optical trap lattice, where the individual intensity profile took LP₀₁mode. This technique flexibly controlled the intensity profile, array dimension, and the hopping over trap lattice. We reported a new 2-dimensional optical trapping by means of the proposed system providing superior benefits in flexible digital control. In order to identify the possibility of optical trapping using the proposed device, single optical trapping was proposed. We demonstrated a polystyrene bead was attracted to a focused beam spot when the focused beam was near by the polystyrene bead and trapped bead was fixed by moving the sample stage of microscope up and down or right and left.

Terahertz transmission filters have been manufactured by perforating metal surface structures with various geometric shapes which all support near-unity transmission at specific frequencies determined by geometric shape, symmetry, polarization, and lattice constant. Our results show that the structures specifically designed by the shape resonance are extremely versatile, dependable, easy to control and easy to make the multifunctional filters.

We report optical amplification in a bismuth-doped silica glass and fiber at 1300 nm region. The optical gain was obtained in a bismuth-doped silica glass at five different wavelengths between 1260 and 1360 nm and the amplification bandwidth was greater than 75 nm. This new gain medium is expected to be useful for application in ultra-wide broadband optical communication. A 5.8 dB gain was observed at 1308 nm in an 8.0 cm bismuth-doped silica fiber. A launched pump power of 152 mW was obtained using an 810-nm laser diode. Simultaneous amplification of two signals from a dual-wavelength near 1300 nm region, the closest to the important telecommunications window, was also achieved. This technique can be used for wavelength division multiplexing optical amplifiers at 1300 nm, which is the range of zero-dispersion for silica fibers.

The amplification mechanism of ultra-wide-band telluride-based fiber Raman amplifier (T-FRA) is analyzed by comparing the stimulated Raman scattering (SRS) characteristics of the telluride-based fiber with silica-based fibers. Then a multi-pumping scheme to get a gain-flattened FRA is presented. We calculate the pump power in designing multi-wavelength pumped Raman amplifiers by using some optimal searching method such as genic algorithm and an effective linear multi-steps method based on average power called Adams-Bashforth method is proposed which not only utilizes former multi-steps known information to get higher accuracy but also avoids iterative scatting by using forecasting-correcting policy The search time of genic algorithm is about 8 minutes and the calculation time is 2 to 3 minutes. The optimizing process of six pumps can be completed within 20minutes and the time may increase if we use 'shot' method. Furthermore, a complete computing model is established to optimize the pump wavelength and power allocation with flat net gain and broad bandwidth. As a result, using telluride-based fiber Raman amplifier, the gain over 10dB from 1500nm to 1620nm (C and L band) is obtained and the gain spectra is more flat especially in C band.

The design criteria of the Panda-type erbium-doped polarization-maintaining fiber (EDPMF) are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. The structural parameters are optimized in terms of the design criteria. A Panda-type EDPMF has been manufactured. The fabrication process and the parameter control of the Panda-type EDPMF are in detail described. Its refractive index profile, birefringence and absorption spectra are experimentally investigated.

The novel multi-wavelength SOA-fiber laser based on a linear- or ring-cavity incorporating a few-mode fiber Bragg grating or a sampled chirped fiber Bragg grating, respectively, is demonstrated. The proposed SOA-fiber laser offers advantages such as simple structure, low loss, multi-wavelength lasing lines with moderate output power.

Two methods to achieve dual-wavelength switching in a fibre laser are proposed and two corresponding switchable dual-wavelength fibre lasers based on fibre Bragg grating (FBG) feedback are demonstrated in this paper. In one proposed fibre laser, both Raman and Erbium-doped fibre (EDF) pumps are employed and the dual-wavelength switching is achieved by controlling the power of the Raman pump. In the other proposed fibre laser, an injection technique is used and the dual-wavelength switching is realized by controlling the power of the injection laser. The detailed behavior of the dual-wavelength switching in the two fibre lasers is experimentally studied and the principle is explained physically.

A dual-pump 10 GHz mode-locking erbium-doped fiber laser was demonstrated. With 10-GHz signal modulation of the modulator, less than 12 ps mode-locked pulse at 10 GHz repetition rate with 1.097 mW average output power was obtained. The corresponding spectrum width is 0.277 nm, which is centered at 1561 nm. The corresponding product of time and bandwidth is Δv*Δt which equals 0.433. Gaussian pulse shape is assumed, the output pulse is almost transform limited. Compared with single-pump fiber ring laser, the dual-pump fiber ring laser is helpful for suppression of supermode noise, which make this kind of fiber ring laser more stable.

In the paper, we have numerically studied how the initial conditions influence the mode-locked soliton formation in the passively mode-locked fiber laser by using the nonlinear polarization rotation technique. We find that once the laser gain is fixed, a soliton with fixed peak power and pulse width will be formed, which is independent of the initial seed pulse conditions. Further numerical simulations have shown that both the peak power and the pulse width of the mode-locked soliton are varied with the linear cavity delay bias setting. We identified that the larger the linear cavity phase setting, the higher the soliton peak and the narrower the soliton pulse achievable in certain range, and adjustable pulse width passively mode-locked fiber laser can be formed by turning the linear cavity delay bias.

Modulation instability in a fiber soliton ring laser is studied by a linear stability analysis of the underlying nonlinear Schroedinger equation. Based on the modulation instability theory and the multisection fiber theory, we achieve the gain flattening in the fiber soliton ring laser. We find that the perturbation gain can be improved when the erbium doped fiber is in the normal dispersion region. When the erbium doped fiber is in the anomalous dispersion region, the perturbation gain spectrum will evolve into a supercontinuum which is similar to a parabola as the small-signal gain of the erbium doped fiber increases.

We will present recent progress in several devices based on silicon-on-insulator nanophotonics using deep-UV lithography. We will report on high efficiency grating couplers, ultra-compact arrayed waveguide gratings and ring-resonator based biosensors.

In this paper, the index guide and band gap guide polymer microstructured optical fibers are designed. For the index guide fiber, a liquid crystal core is used and 60dB extinction ratio tunable attenuator is obtained. For the bandgap polymer microstructured optical fibers, a regular structure is presented from experiment and an ideal defect can be realized easily by a new method.

The Q-factor of the optical nanowire microcoil resonator is calculated and compared for different geometries. The results suggest that the Q-factor is very sensitive to the coupling conditions and high-Q resonators can be obtained more easily when the geometry of the nanowire microcoil resonator or its coupling contour has a bi-conical profile.

The transmission of a one-dimensional left-handed photonic crystal consisting of alternating slabs of two materials with positive and negative refractive index respectively is investigated with the help of transfer matrix method (TTM). The properties of defect modes of the left-handed photonic crystal were disclosed. Both the number and the location of defect modes strongly depend on the property and composition of defects. The defect modes resulted from negative defect often appears in the zero average refractive index (ZARI) gap, while those resulted from positive defect usually appears in the Bragg gap. The defect modes, no matter in the Bragg gap or in the ZARI gap, exhibit degeneracy and split as the distance between the two defects decreases. Due to the coupling of the two defects, the split of defect mode does not appear when two different kinds of defect are introduced.

A novel single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed through a full-vector finite element method (FEM) with anisotropic perfectly matched layer (PML). Numerical results show that the proposed fiber is a low-loss SPSM-PCF within wavelength range from 1370 to 1610nm, in which only the slow-axis mode is guided and the confinement loss is below 0.1dB/km.

A method for judging mode cutoff in photonic crystal fibers (PCFs) with non-uniform holes by analyzing the break phenomena of the mode field radius during the increasing of wavelength is brought forward. And three kinds of PCFs with different structure are analyzed and discussed in detail using this new method.

Mode properties of two different types of six-hole holey fibers were analyzed using the plane wave expansion (PWE) method. Calculated results suggest that a variety of waveguide dispersion characteristics may be obtained from these structures with a suitable choice of hole shape, size and pitch values. In addition, mode field diameter (MFD) and splice loss due to the MFD mismatch were calculated.

The paper investigate the effect and control of loss for the beam propagation in Kerr-type nonlinear optical lattices, and the loss compensation by the longitudinal depth of the modulation analytically and numerically. It is shown that media loss reduce the peak power of lattice soliton, decreasing the nonlinear effects, disturbing the balance between the diffraction and nonlinear effects. As a result, lattice soliton can't propagate steadily and optical beam dispersed finally. It is possible that proper changing the longitudinal lattice depth can complete suppression of the loss's influence and the beam can be regenerated successfully. There are analogy characteristic in the action of periodic lattice's potential of optical and nonlinear. The periodic potential offers the better method to control the lattice soliton formation and propagation.

The characteristics of femtosecond pulse trapping in photonic crystal fibers are investigated. Numerical simulations show that the efficiency of pulse trapping can be improved by adjusting the parameters of pump pulse. For a given pulse width, the trapping efficiency is fluctuant as the temporal delay increases and has a maximal value. The blue-shift of signal pulse and the red-shift of pump pulse, however, have no matter with temporal delay. The maximal trapping efficiency and the corresponding temporal delay both decrease as the pulse width increases.

Transmissive-Writing and Orthogonal-Readout scheme (TWOR) is proposed for making wavelength filters in holographic media sensitive to wavelengths far shorter than that for fiber communication. The optimization of device performances through this scheme is also discussed. Preliminary experiments on angular selectivity of a volume grating verified the feasibility of this scheme.

One time division multiplexer based on half-reflective coating lens as beam splitter/combiner and fiber length to control relative time delay between two channels was demonstrated and experimentally studied in detail. This time-division multiplexer is a serial structure with four stages, and a pulse stream with sixteen times repetition rate can be achieved with the multiplexers. Its characteristics including polarization properties were experimentally studied in 16×10 Gb/s optical signal generation system.

A temperature-insensitive quartz cavity Fabry-Perot etalon is used in an angle-tuned optical filter. A new high precise orientation technique is introduced to locate the etalon angle precisely based on a position sensitive detector. The tunable optical filter has high temperature-stability, perfect repeatability and high resolution. The repeatability precision is better than 0.01 nm. The resolution is 0.004 nm.

Based on Er-Yb co-doped phosphate glass substrate, tunable single micro-ring filter using thermo-optic effect is proposed and analyzed theoretically. The analytical expressions of the transmission performance, bandwidth and finesse of the proposed ring resonator filter are derived using transfer matrix method, the calculated temperature coefficient of center wavelength is 0.011nm/°C. Numerical results demonstrate that bandwidth and finesse of the filter can be adjusted by varying the input pump power.

A new method to create a long-period fiber grating utilizing a scanning CO2 laser with varying scanning velocities is reported that results in strong grating (>30dB loss) with extremely short grating length (1.1-cm) all achieved with low insertion loss (<2dB).

A novel technique for dispersion compensation is presented. Based on the theoretical analysis, an ideal instance of characteristics of linear chirped fiber Bragg grating (CFBG) with 11 thermal heads and a laboratory instance of characteristics of the CFBG with 5 thermal heads varies with different temperature is shown. They are analyzed at room temperature with variation of the decrease from 3°C to -3°C and the increase from -2°C to 2°C. According to the results of the simulations based on theoretical analysis, the change of micro-heaters temperature will induce the change of grating temperature, and then change the Bragg wavelength, delay and delay slope of the CFBG. Further more, a material experiment is presented. These results show that if the temperature controller is good enough, we will be able to limit the temperature from 0°C to 4°C and we will receive some random dispersion values from -2608.2ps/nm to - 2835.6ps/nm. Therefore, this dispersion compensator can compensate the survival dispersion completely and can be applied to the long-distance transmission and the optical communication system.

We propose and experimentally demonstrate long-distance, simultaneous measurement of strain and temperature based on a Raman fiber laser with a single FBG embedded on a quartz plate. Most of all, FBG based sensing technology has attracted considerable attention in the field of optical sensors since FBG based sensing probe can provide the most simple and attractive methods to monitor the external perturbation change like temperature, strain, and pressure due to its high sensitivity, electro-magnetic immunity, compactness, and ease of fabrication. In order to enhance the measurement resolution of sensing systems, fiber lasers based sensor schemes with narrow bandwidth and high extinction ratio have been considered as promising technologies. A novel and practical Raman laser based long-distance sensing scheme for simultaneous measurement of strain and temperature using FBGs is investigated. High-quality Raman laser output with a high extinction ratio of more than 50 dB is obtained at a long distance of over 50 km. Lasing wavelength shift and separation occur as the temperature and strain increase, respectively. To induce these phenomena, half of the FBG is fixed steadily on the quartz plate to respond to temperature only, while the other half of the FBG is free to respond to both temperature and strain. The temperature and strain sensitivities are measured to be 8.96 pm/oC and 1.47 pm/ustrain, respectively. This allows simultaneous measurement of strain and temperature for long-distance sensing applications of more than 50 km.

Proposed and demonstrated in this letter is a scheme of fiber Bragg grating (FBG) sensor interrogation system based on all fiber Mach-Zehnder Interferometer (MZI) edge filter and tunable-FBG, of which the Bragg period is tunable through a one-dimensional adjustor. Wavelengths message of FBG sensor and the tunable-FBG are transformed into powers message by a pair of the filtering edges of the filter, respectively; and the wavelength difference between the FBG sensor and the tunable-FBG can be obtained through differing the two pairs powers message. In measured experiments, the results show that the precision of the proposed system is 0.02nm in a range of 1nm. The wavelength measurement range can be improved by adjusting the length difference of the two interference arms of the filter.

Diffractive optical gratings (DOGs) are designed for implementing beam splitting and wavelength demultiplexing simultaneously by the use of conjugate gradient optimization algorithm. A plane wave with multi-wavelength is demultiplexed and spatial splitled into the predesigned wavelengths and directions by the designed diffractive optical gratings. The numerical results show that the designed multi-functional DOGs can successfully generate desired wavelength at predesigned directions. It indicates that the DOG can be flexibly designed for realizing desired optical function. It is believed that this design can provide a useful information for designing the wavelength division multiplexer and the arrayed waveguide grating in various optical system.

The cladding mode generated by the tilted fiber Bragg grating is out-coupled to optical power detector by the total internal reflection at the micro-etched cladding. Optimization of the tilted fiber Bragg grating and micro-etched cladding for high efficient out-coupling of cladding mode was discussed theoretically. Over 32 % power of the cladding mode is out-coupled by the micro-etched cladding. In addition, as much as 90 % power of the input power is experimentally detected using the avalanche photodiode.

The buried channel waveguides on optical glass is fabricated by a high electric field technique. The 900V voltage was applied on the glass to accelerate the field-driven ion exchange process by expeditiously replacing host sodium ions in the glass with silver ions. As a result, the lowest optical loss was achieved on waveguides fabricated at 350°C. The optical loss for channel waveguides was measured using the interference technique with a 0.6328μm He-Ne laser. And the loss of 0.30 dB/cm was obtained for channel waveguides of 20μm in depth, relatively low for waveguides of such depth at red wavelength. A nearly Gauss refractive index profile was observed from every channel waveguide fabricated.

We present a novel all-optical header and payload separation technique that can be utilized in Un-Slotted optical packet switched networks. The technique uses two modified TOADs, one is for packet header extraction with differential modulation scheme and the other performs a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is simple structure and low power consumption. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the system parameters are discussed and designed to optimize the performance of the proposed scheme.

The transmission properties of a uniform Fiber Bragg Grating (FBG) in a photonic crystal fiber (PCF) with C6v symmetry are studied in this article. The Bragg wavelength λB, increases asymptotically to a particular wavelength as the number of air-hole ring or the hole pitch Λf increases; on the contrary, it decreases as the relative hole size (hole-pitch ratio f) increases. The coupling coefficient between the forward and backward propagating fundamental modes decreases as Λf increases and increases as f increases.

This paper have successfully demonstrated an all-optical wavelength conversion scheme for all-speed return-to-zero (RZ) format data input by using a Sagnac interferometer based on semiconductor optical amplifier (SOA).The attractive issue of the proposed method is that the converted signal can be obtained simultaneously with inverted and noninverted wavelength conversion signals.

Time independent rate equations for fiber laser are solved accurately with numerical method under multipoint boundary conditions. A novel method based on genetic algorithm is firstly proposed to optimize distributed pump powers and fiber segment lengths of kilowatt YDDC fiber laser. The uniformity of temperature distribution is improved by using optimized method. The calculated results show that the lower operating temperature and better uniformity can be obtained through increasing the number of segments at the cost of decreased output signal power.

A novel structure for efficient side-coupling of high power double-cladding fiber laser is presented. The maximum coupling efficiency of this structure is more than 90% for TM-polarization in +1 and -1 order but is only 40% for TE-polarization. Thus, a two-layer structure is introduced to obtain higher coupling efficiency for TE-polarization and maximum coupling efficiency almost 70% is demonstrated.

We propose an analytical reflection model for the waveguide switch with total-internal-reflection structure, which is the grazing reflection of beam with narrow beamwaist. For such incidence condition, the output optical field is the superposition of incident and reflected fields, we deduce the effective reflection coefficient together with angular spectrum of the output field.

Erbium-doped photonic crystal fiber (EDPCF) is not in the endless single-mode as the refractive index of the core in EDPCF is higher than that of silica cladding. There is a variation between the EDPCF and the conventional PCF. The modified average population inversion iteration method is proposed for simulating the gains and noises of EDPCF amplifiers. The effect of the structural parameters of EDPCF on the cutoff wavelengths, splice loss and the amplification properties is studied in detail by means of the improved average population iterative method combined with the finite element method. According to the design criteria of erbium-doped fiber, the four structural parameters of EDPCF-core radius, the refractive index difference between the core and silica cladding, the relative size of the core and the relative size of air holes are optimized.

The temperature and stress characteristics of double-clad fiber Bragg grating are investigated, respectively. The thermal decay characteristics according to the different anneal thermal, 100°C, 150°C, 200°C and 250°C are got. These results are very significant to estimate the properties of grating, such as thermal, wavelength and anneal time. Birefringence effect of the grating is also detected in rectangular inner cladding DCF gratings. By applying stress on the grating, strain is induced. One reflection peak of double-clad fiber Bragg grating becomes two peaks. The relation between the stress and the peak shift is obtained. The two reflection peaks can be tuned from 0 to 0.8nm. These results are more significant for estimate the sensor properties of the DCF Bragg gratings.

Based on PCVD deposition process and Rod-In-Tube draw process, highly nonlinear fibers were designed and fabricated for efficient fiber nonlinearity generation. Highly nonlinear fibers employed high-concentration GeO2-doped core and fluorine-doped cladding were simulated, in which key structure parameters were investigated, such as the core diameter, core profile shape, and the b/a. The fabricated fibers successfully realized a low attenuation less than 1.30dB/km with an effective area of about 10um² and a dispersion slope about 0.020ps/nm²/km at the operating wavelength of 1.55um. For different applications such as Raman amplifier and four-wave mixing (FWM) generation, a series of fibers were fabricated with different dispersion spectrums in the S+C+L-band. Some application experiments were also introduced, which were related to fiber properties. Our fabricated fibers achieved the maximum effective Raman gain coefficient of 5.08W^-1km^-1 and the nonlinear coefficient of 12W^-1km^-1.

The Ethernet Passive Optical Network (EPON) has recently attracted more and more research attentions since it could be a perfect candidate for next generation access networks. EPON utilizes pon structure to carry ethernet data, having the both advantages of pon and ethernet devices. From traditional view, EPON is considered to only be a Ethernet services access platform and wake in supporting multi-services especially real-time service. It is obvious that if epon designed only to aim to carrying data service, it is difficult for epon devices to fulfill service provider's command of taking EPON as a integrated service access platform. So discussing the multi-services carrying technology in EPONs is a significative task. This paper deploy a novel method of multi-llid to support multi-services carrying in EPONs.

The finite element method with 2^nd-order transparent boundary conditions is proposed to analysis the modes of photonic crystal fibers. These boundary conditions preserve the sparse matrix and offering accuracy of O(r^-9/2), here r denoting the position of the computational boundary with respect to a chosen origin of the structure. The effective mode-index, the mode distribution, the confinement loss and the dispersion properties of the total internal reflection photonic crystal fibers (TIR-PCF) with triangle lattices and rectangle lattices are calculated in this method respectively. The results agree with the published results. At the same time the finite element method in the paper lessens the computation domain remarkably. It offers an easy and credibility approach in the study on the PCF and other fibers with irregular cross-section index distribution, even fibers with anisotropy materials.

Based on self-stability effect of four-wave mixings in high-nonlinear photonic-crystal fibers, multi-wavelength erbium-doped fiber lasers are proposed and demonstrated experimentally at room temperature. The proposed lasers have the capacity of switching and tuning with excellent uniformity and stability

Recently a significant advancement in THz source and detector technology have arisen a number of potential application such as space-based communication, THz sensing and imaging for military and security, biology and so on. However, THz spectroscopic techniques uses mainly free space propagation and guided wave still remains a challenge in this intermediate spectral region. In this paper, a square lattice microstructure terahertz waveguide is proposed. Combining super-lattice full-vector method with beam propagation method, its optical properties, especially dispersion, confinement loss and single mode property, are analyzed. Numerical results demonstrate that this waveguide can operate at single mode with low dispersion and low confinement loss.

We fabricated linearly chirped fiber gratings by using uniform phase mask instead of chirped mask. The chirp of the grating is realized by precisely setting the distance between the fiber and the phase mask at every point of the fiber. In experiments we derived linearly chirped fiber grating which has dispersion -1102ps/nm, time delay ripple is 17ps. And also the asymmetry high order apodization method is used successfully to reduce the time delay ripple. The experiment results consistent with the simulation results. We can fabricate gratings with different chirp extent use one uniform phase mask conveniently by only changing the curve function of the fiber.

This work is motivated by the need to ultra-short optical pulses for realizing OTDM/WDM. As an attractive ultra-short pulse source, the mode-locked fiber laser attracts more and more attentions. In this paper, we proposed a novel method to design passively mode-locked fiber laser by combining lumped-gain amplification and high output couple ratio. On the one hand, through using lumped-gain amplifier as the amplifying units in the cavity, the mode-locked fiber laser can effectively reduce the periodic energy fluctuation of intra-cavity and offer a very good suppression to the spectral sidebands. On the other hand, a coupler with high output couple ratio is used in the cavity to enhance the output single-pulse energy. The characteristics of the presented laser have been investigated theoretically and experimentally in detail. With this method, a passively mode-locked Er³⁺-doped fiber laser with high spectrum quality and high single pulse energy is obtained. The experimental results show that its spectral sidebands suppression ratio is more than 20dB, the maximum average output power is about 18mW and the single pulse energy is about 1.2nJ with pulse-width 200fs at a repetition of 14.2MHz.

Several measurement methods for polarization dependent transmission in an optical fiber link are compared. The relationship between these methods is discussed. Guidelines for choosing a particular method are provided based on accuracy, speed, and system characteristics.

We have demonstrated an all optical switching by use of pulse trapping in photonic crystal fiber (PCF). A train of four pulses with temporal separation of 1 ps is used as the signal pulses, in which only one pulse is trapped by the soliton pulse in the PCF. The wavelength of the trapped pulse is blue shifted, and thus the trapped pulse can be picked off easily by use of a wavelength filter such as a fiber Bragg grating. In addition, The characteristics of the ultrafast all optical switching are analyzed numerically. The trapping efficiency decreases as the temporal separation increases. The low trapping efficiency impairs the performance of optical switching.

A theoretical investigation of the pulse trapping in a birefringent photonic crystal fiber is presented. The strict coupled nonlinear Schroedinger equations are solved numerically using a standard split-step Fourier algorithm. Different phenomena of pulse trapping are observed depending on whether the two pulses are polarized along the same polarization axes. The signal pulse suffers cross phase modulation (XPM) from the pump pulse and it is trapped to copropagate with the pump pulse along the fiber. Much larger wavelength shift of the trapped signal pulse can be obtained by increasing the power of pump pulse. Different initial temporal separation between the pump pulse and the signal pulse leads to different effect in the pulse trapping.

We show that the extinction ratio is improved using slight asymmetry in two core refractive indices of polarization independent very short vertical directional couplers with the double-sided deep-ridge waveguide structure. The optimum asymmetry with the maximum extinction ratio increases as the thicknesses of the inner cladding layer and the two core layers decrease. Also, the device length and the tolerance of the device length with the extinction ratio more than 30 dB decrease as the thicknesses of the inner cladding layer and the two core layers decrease.

In this paper, several triangular-lattice highly birefringent PCFs are analyzed on the base of the full vector model. Several properties of them, such as the PCF's modal field, the birefringence and the dispersion, are simulated by the supercell lattice method. Moreover, a comparison is made among them to study the impact of air-holes configuration of PCFs on their propagation properties. The simulation results show that air-holes at different position have different impact on the propagation properties of PCFs.

Polarization mode dispersion vectors measurement methods are integrated into a unitive theoretical model. A clear comparison among these methods is conducted to clarify their advantages and disadvantages. Experimental results on optical fiber systems with and without PDL/G are implemented to compare these methods.

We investigate the focusing performance of a closed-boundary axilens with long common focal depth by boundary integral euquations. The common extended focal depth of a cylindrical micro-axilens, illuminated by different incident wavelengths is numerically simulated, and the electric field intensity distribution is numerically determined by the boundary element method. The results show that the long common focal depth is changed when the preset focal depth is increased.

Here we demonstrated a dispersion stretched passively mode-locked fiber laser. The laser was mode-locked by nonlinear polarization rotation (NPR) technical. Both dispersion managed soliton and noise-like pulses were observed in the experiment. Harmonic mode-locked noise-like pulses were observed. By changing the pump power or rotating the waveplates, noise-like pulse could split and always form equally spaced pulse train, thus the repetition rate of the output pulse could be switched among different orders of harmonic frequency. The experiment results were analyzed. We found that peak power clamping caused by NPR module led to pulse splitting, the pulse interaction through the Raman light drives the pulse to space equally.

A method of writing long period grating and a model to explain light coupling between fundamental mode and cladding mode are presented. One athermal hermetic sealing approach is proposed to form hermetic sealing long period fiber grating. A long period fiber grating was designed and written for this experiment. Low temperature glass solder was introduced to seal around the fiber. The sealing and optical performance testing results are discussed.

We propose a simple method to improve the spectral sensitivity and detection limit of long period grating sensor for chemical sensing, in which the grating surface is modified by colloidal gold nanoparticles. The transmission spectra and optical properties of gold nanospheres change with the different refractive index of the environment near the surface of gold nanospheres. The sensor response of gold colloids increases linearly with solvents of increasing refractive index. The results for the measurement of sucrose solutions showed that the slope of wavelength shifts increased from -18 (nm/RIU) to -24 (nm/RIU); while for changes of peak depth, its slope increased from 37 (dB/RIU) to 60 (dB/RIU). The accuracy of concentration measurement for salt water solution was increased from 0.6% to 0.2%, and limit of detection can be improved from 0.04% to 0.02%. When the colloidal gold surface was modified with a dimitrophenyl compound (DNP), results showed that the signal increase linearly with increasing concentration of the analyte, and the detection limit of the sensor for anti-DNP is 9.5×10^-10 M.

System performance degradation caused by group delay ripples of chirped fiber Bragg grating dispersion compensators is analyzed in detail with considerations for the ripple period, amplitude and phase offset. And the induced different kinds of signal distortions are also shown and explained.

Giving a new method to tuning a fiber Bragg grating into a chirped grating using a gradient curvature beam. Stick a FBG to an "S" shape beam with one end free and another give a pull. The curvature of the beam would change and the FBG get gradient strain. Thus we get the chirped grating while the central wavelength doesn't change. The design method and the theoretical analysis are given. The maximum chirped bandwidth in our experiment is 5.10nm and the central wavelength does not change.

In this work, the experimental analysis of the sensitivity characteristics to the surrounding refractive index in nanoscale coated long period gratings (LPGs) is presented. Polymeric coatings of refractive index higher than the cladding one have been considered with thickness values ranging in hundreds of nanometers. The presence of the high refractive index coating induces the cladding to overlay mode transition depending on the overlay features (thickness and index) and the surrounding refractive index. The immediate consequence is a drastic enhancement in the sensitivity to surrounding refractive index due to a large shift of all the attenuation bands in the refractive index range where the modal transition occurs. As matter of fact the sensitivity characteristics changes from the sub-linear monotone behaviour to a resonant like shape. Here, a complete experimental analysis combined with an analytical fitting has been investigated to outline the new SRI sensitivity profile and its dependence on the overlay thickness and order mode.